OBJECTIVE: To determine if the spleen cells of male and female mice demonstrate differences in immune responsiveness to mitogenes at various states in the life cycle from birth to old age. In addition, the effect of sex steroids on the immune responsiveness of lymphocyte function will be determined in the intact and castrate male and female mice at the various age groups. Prostaglandin levels will be measured at different ages in lymphoid tissue to determine, not only if sex differences in prostaglandin levels exist, but also if such differences are affected by castration and the administration of the sex steroids and prostaglandin synthetase inhibitors. An attempt will be made to correlate the prostaglandin levels with immune function, sex, and age.